Note: Descriptions are shown in the official language in which they were submitted.
ABSORBENT MIXTURE, METHO~ OF MAKING
SAME, AND ABSQRBENT ARTICL~ INCLUDING SAME
Technical Field_of the_Invention
This invention pertains to an absorbent
mixture co~prising superabsorbent particles and
fragments of superabsorbent polymer bo~nd to fibrous
materials, and to an absorbent article including such
a mixture. This invention pertains also to a method
of making such a m;xture. Since the absorbent
mixture is capable of absorbin~ liq~id human excreta,
such as urine, menses, and wound excreta, the
absorbent mixture may be advantageously employed in
making an a~sorbent article useful in a disposable
diaper, tampon, sanitary napkin, wound dressing, or
similar article.
Background of the Invention
Detailed diccussions of absorbent articles
employing superabsorbent materials in disposable
diapers and other products are included in Pieniak et
al. U.S. Patents ~o, 4,500,315, No. 4,S40t454, No.
4,537~590, and No. 4,573~988, which collectively
provide useful baclcground for this invention.
As discussed in the Pieniak et al. patents
noted above, absorbent articles can be advantageously
made with absorbing layers and wicking layers. The
a~sorbing layers can ~e advantageously made from
polyester fibers, within which particles of
superabsorbent material are dispersed. The wicking
layers can be advantageously made from cellulosic
fibers; which can include or be provided in the form
of a densified, paper-like la~er, ~uch as is
disclosed in Bur~eni U.S~ Patent No 3,017,3G4, on
one side or each side. Seet also, Mesek et al. U.S.
Patent No. 3~612,055 and Repke U.S. Patent No.
3jg38~22.
?~s~
~2
As also discussed in the Pieniak et al~
patents roted above the superabsorbent ma~erial can
be advantageously formed from a polymerizableg
cross-linkable material, e.g., a ~ater-soluble
monomer exemplified by sodium, potassium, or aTrunonium
acrylate, which is coatedf in a liq~id carrier, e.g.,
in an aqueous solution~ onto a fibrous webi and which
is polymerized and cross-linked in situ, so as to
form a hydrophilic polymer, which has superabsorbent
properties.
Conventional coating techniques involve
flooding the fibrous web with the material, in the
liquid carrier, while the fibrous web is supported on
a screen, so as to saturate the fibrous web, and
exposing the saturated web to a partial vacuum, which
removes excess amounts of the material, in the liquid
carrier. It has been heretofore known to remove
excess amounts of liquid by means of a padder or
squeeze roll, after the fibrous web has been
saturated, with similar results.
As an alternative to conventional coating
techniques discussed above, it has been heretvfore
known to spray droplets of such a material, in a
liquid carrier, by means o nozzles.
It also has been heretofore known that
polymerization and cross-linking in situ can be
advantageously effected by electron beam
irradiation. Other techniques for polymerizing and
cross-linking have been hereto~ore known, e.g.,
chemical initiation, which may require a catalyst or
initiator o~ a known type, and heating by
conventi~nal heating means.
Although the Pieniak et ~1. patents noted
above disclose useful products and useful methods of
3~ manufac~urin~ such products~ there has been a need,
~t ~
heretofore, for absorbent articles offering superior
wicking and ahsorbent properties.
Herein, each reference to a polymerizable,
~ cross-linkable material, in a liquid carrier, is
intended to refer to any suitable monomer, oligomer,
or polymer of low molec~lar weight, as exemplified by
but not limited to a sodium, potassium, or ammonium
salt of acrylic or methacrylic acid, together with a
sufficient quantity of any catalyst or initiator
needed to catalyze or init;ate polymerizing and
cross-linking of the monomer, oligomer, or polymer of
low molecular weight, in a solution or s~spension in
a liq~id carrier, as exemplified by bu~ not limited
to water. Moreover, as and where appropriate, each
reference to a polymer is intended to refer to a
heteropolymer or a polymer of a usual structure.
Herein, each reference to a ~aterial having
absorbent properties is intended to refer to a
material capable of absorbing liquid human excreta,
such as urine, menses, or wound excreta. Moreover,
each reference to a material having superabsorbent
properties is intended to refer to a material capable
of absorbing many times its own weight of s~ch human
excreta.
Summary of the Invention
~ . ~ .
This invention provides an absorbent m! xture
having superior wicking and absorben~ properties~
Broadly, the absorbent mixture comprises first
particles, each ~omprised of a polymerized,
cross~linked material haviny absorbent properties,
an~ second, two-phase particles, each havin~ a
fibrous phase comprised of fibers and a polymerized,
cross-linked phase comprised of fragments of such
material bound ~o fibers of ~he first phase. At
3~ least some of the first pzr~icles and at least some
Z0167~J~?.
of the fragments are broken from larger particles of
such material. The absorbent mixture may be
advantageously employed in the manufacture of an
absorbent article useful in a disposable diaper,
tampon, sanitary napkin, wound dressing, or similar
product req~iring high absorbency.
According to this invention, the absorbent
mixture is made from fibers formed into a fibro~s
body, e.g., a nonwoven web, and a polymerizable,
cross-linkable material, in a liquid carrier. Fibers
of many different types are useful, such as rayons,
cellulose esters, proteins, polyamides, polyestèrs,
polyvinyls, polyolefins, polyurethanes, glass, and
mixtures thereof. Polymerizable, cross-linkable
materials of many different types having absorbent or
superabsorbent properties when polymerized and
cross-linked, in liquid carriers, are useful, such as
a sodium, potassium, or ammonium salt of acrylic or
methacrylic acid, in an aqueous solution wherein
water is the liquid carrier. S~ch a salt, when
polymerized and cross-linked, results in a
superabsorbent polymer.
The polymerizable, cross-linkable material,
in the liquid carrier, is dispersed within the
fibrous body, as dispersed inclusions. The
polymerizable, cross-linkable material is polymerized
and cross-linked in situ, within the fibrous body, so
as to form a composite body. The composite body
comprises the fibrous body and the polymerized,
cross-linked materal, as dispersed particles, at
least some of which are bound to fibers from ~he
fibrous web.
The absorbent mixt~re results from the
composite body being ground, so as to cause some of
the polymerized, cross-linked material to become
--5--
particulate, as powder or granules, whereby the first
particles are formed, while fragments of the
polymerized, cross-linked material remain bound to
fibers from the fibro~s body, whereby the second
particles are formed. The material that becomes
particulate and the material that re~ains bound to
fibers from the fibrous web account for the
polymerized, cross-linked material bound to fibers
from the fibrous web, in the composite body before
the composite body is ground.
The composite body may be optionally
provided, before it is ground, with at least one
layer of fibers for~ed into a fibrous layer in
intimate contact with the fibrous body having sucn
inclusions. Such a layer may be optionally provided
on each side of the fibrous body having such
dispersed particles. If so, the fibers of the
fibrous layer, or fibro~s layers, may be
advantageously made from comminuted wood pulp. The
composite body may be intermediately processed, e.g.,
compressed, before the composite body is ground.
Fragments of the polymerized, cross-linked
material remain bound to fibers from the fibrous body
and strengthen the fibers to which such fragments are
bound, whereby particulates having fibrous matrices
including such strengthened fibers tend to retain
their bulk when wetted with ~ liquid being absorbed,
e.g., with urine being absorbed in a d;sposable
diaper. Hence, the absorbent mixture exhibits
superior wicking properties with less tendency for
gel blocking. Gel blocking oCGUrS if parti~les of a
superabsorbent polymer tending to form a gel when
swelling with a liquid being absorbed are ~oo densely
distributed within an absorbent article, so that the
~welling particles ten~ to form a gel layer, which
blocks addition~l liquid from penetrating.
The absorbent mixture exhibits superior
absorbent properties, not only ;n terms v~ its
efficiency as absorbent material but also in terms of
its rate of absorbency, particularly as compared to
absorbent structures containing similar amounts of
fibers of the same types and in the same ratios and
similar amounts of a superabsorbent polymer of the
same type, on a weight basis. The absorbent mixture
may be advantageously employed, therefore, in the
manufacture of an absorbent article useful in a
disposable diaper, tampon, sanitary napkin, wound
dressing, or similar product benefiting from superior
absorbency.
These and other objects, features, and
advantages of this invention are evident from the
following description of a 2referred mode for
carrying out this invention with reference to the
accompanyin~ drawings.
Brief Description of the Drawings
FIGURE 1 is a flow diagram representing
certain steps in the manufacture of an absorbent
mixture according to this invention.
~IGURE 2 is a fragmentary view taken along
one edge of an absorbent article including layers of
an absorbent mixture manufactured as represented in
FIW RE 1.
FIGURE 3 is a graph showing comparative
properties of two samples, one being a sa~ple of an
absorbent mixture according to this invent;on.
Detailed ~escri~tion of Preferred Mode
~
While the presen~ invention is sus~ep~ible
of embodiment in various fonms, there is shown in ~he
drawings and will hereinafter be described a
presently preferred embodiment, with the
understanding tha~ the present disclosure is to be
~ ~ g~ 7~
considered as an exemplification of the invention and
is not intended to limit the invention to the
specific embo~iment illustrated.
~his invention provides an absorbent mixture
A comprisins a novel mixture of par~icles of two
types, which may be conveniently called first and
second particles, and having s~perior wicking and
absorbent properties.
Each of the first particles is comprised of
a polymerized, cross-linked material having absorbent
properties, preferably a superabsorbent polymer of a
known type used in disposable dla~ers, tampons,
sanitary napkins, or wound dressings, e.g., sodium,
potassium, or ammonium polyacrylate produced by
polymerizing and cross-linking ~ sodi~, potassi~m,
or ammonium salt of acrylic or methacrylic acid, as
provided in an aq~leous solution wherein the salt has
been partially neutralized, and wherein the liquid
carrier is water. A preferred example of such a
solution is a 6$~ concentration (by we;ght) of a 55%
neutrali2ed (on a mole basis) potassium salt of
acrylic acid, as neutralized with a 45% potassium
hydroxide solutionc
Each of the second particles has a fibrous
phase comprised of fibers and a polymerized,
cross-linked phase comprised of fra~ments of the
polymerized, cross-linked material bound to fibers of
the fibrous phase. At least some of the first
particles and at least some of th2 fragments are
broken from larger partieles of such material~ This
invention allows for possibilities that some o the
first particles, some of the fragments, or both are
unbroken. The absorbent mixture A can ~e
advan~ageQusly made by a method to be next described~
3;
7 ~
Initially, a fibrous web W is provided alo~
with a polymerizable, ~ross-linkable material, In a
liquid carrier, from any suitable source S. When
polymerized and cross-linked, the polymerizable,
S cross-linkable material res~lts in the polymerized,
cross-linked material noted above. Thus, an aqueo~s
solution according to the preferred example noted
above may constitute the polymerizable,
cross-linkable material, in the liquid carrier.
The fibrous web W is formed of fibers
selected from rayons, cellulose esters, proteins,
polyamides, polyesters,opolyvinyls, polyolefins,
polyurethanes, glass, or mixtures thereof.
Preferably, the fibrous web W comprises poly(ethylene
terephthalate) fibers of a type having a hollow core,
as available commercially under the trademark
HOLLOFIL from E. I. DuPont de Nemours and Company,
l~ilmington, Delaware, and sheath-core fibers, each
having a core of poly(ethylene terephthalate) and a
sheath of polyethylene, as carded into a nonwoven web
having a basis weight of 1.2 oz/yd2 and thermally
bonded by subjecting the nonwoven web to air heated
to about 275F and pulled through the nonwoven web
while the non~oven web is supported on a screen (not
shown) in a kno~n manner.
In a dispersing zone Zl' the
polymerizable, cross~linkable material, in the liquid
carrier, i5 dispersed within the fibrous web W, as
dispersed inclusions includins the liquid carrier.
30 Conventional coating techniques or alternative
spraying techniques are usef~l to disperse the
polymerizable, cross-lînkable material, in the liqu;d
carrier, within the fibrous web W.
Conventional coating techniques involve
flooding the fibrous web W with the pol~meri~able5
_9_
cross-linkable material, in the liquid carrier, while
the fibrous web W is supported on a screen (not
shown~, so as to saturate the fibrous web W, and
exposing the sat~rated web W to a partial vacuum,
which removes excess amounts of the polymerizable,
cross-linkable material, in the liquid carrier.
Excess amounts of liquid may be alternatively removed
by means of a padder or squeeze roll (not shown),
after the fibrous web W has ~een saturated, with
similar results. Whichever approach is used to
remove excess amounts of liqua~, the fibrous web W
tends to retain the polymerizable, cross-linkable
material, in the liquid carrier, as dispersed
inclusions including the liquid carrier, bridging
adjacent fibers of the fibrous web W, and being held
by fiber-to-fiber capillaries.
If alternative spraying techniq~es are use~
to disperse the polymerizable, cross-linkable
material, in the liquid carrier, within the fibrous
web W, droplets of the polymerizable, cross-linkable
material, in the liquid carrier, may be thus sprayed,
as by means of nozzles, onto opposite sides of the
fibrous web W as the fibrous web W is moved through
the dispersing zone Zl The fibrous we~ W tends to
retain such droplets as dispersed inclusions
inclu~ing the liquid carrier, bridging adjacent
fibers of the fibrous web W, and being held by
fiber-to-fi~er capillaries.
After the polymerizable~ cross-linkable
material M~ ln the liquid carrier, has been dispersed
within the fibrous web W, as dispersed inclusions
including the liquid carrier, the fibrous web W
retaining such inclusions is moved to a polymerizing
and cross-linking zone Z2~ in which the material M
is polymerized and cross-linked an situ, within the
~ç~
10-
fibrous web W, so as to form a composite web W
comprising the fibrous web W and the polymerized,
cross-linked material, as dispersed particles, some
most, or all of which are bound to fiber~ from the
fibrous web W. This invention allows for a
possibility that s~me of ~he dispersed particles may
not be so bound but may be loosely retained within
the composite web W'. Rowever, dispersed particles
bound to fibers from the fibrous web W constitute the
larger particles noted above, from which at least
some of the first particles and at least some of the
fragments are broken.
Any suitable means (not shown) for electron
beam irradiation is preferred as a means for
polymerizing and cross-linking the material M; an
example is an Energy Sciences TM ~Model CB3003
accelerator, as availahle from Energy 5ciences, Inc.
If electron beam irradiation is used, the fibrous web
W retaining the material M, in the liquid carrier, in
dispersed inclusions may be initially exposed to 2
MRAD of such radiation on each side of the fibrous
web W, and f inall y exposed to a curing dose of 8 MP~D
on each side of the f ibrous web W. Any other
suitable technique for electron beam irradiation may
be instead used.
Any other suitable technique for
polymerizing and cross-linking the material M in situ
may be instead used, e.g.9 chemical initiation9 which
may require a catalyst or initiator of a known type.
The comp~site web W' cvntains dispersed
parti~les of the polymerized,. cross-linked material M
fram which substanti~lly all of the liguid carrier
has evolve~ the polymerizable, cross~linkable
material, in ~he liquid carrier, 1s an aqueous
3~ sol~tion according to the preferred example given
2016~
--11--
above, such particles are comprised of sodium
polyacrylate, from which substantially all of the
liquid carrier, i.e., water, has evolved.
The composite web W' may be intermediately
processed in known ways. The composite web W' may be
provided, on each side, with a fibrous Iayer, e.g., a
nonwoven layer of fibers from comminuted wood pulp or
other cellulosic fibers, in intimate contact with the
fibrous web having such inclusions of the
polymerized, cross-linked material. The facing
layers may be also provided with a densified,
paper-like layer (not shown1 in a manner disclosed in
the Burgeni, Mesek et al., and Repke patents noted
above. Moreover, the composite web W' may be then
compressed, so as to increase its density.
It is to be here understood that the
composite web W' is made and may be intermediately
processed by methods similar to methods disclosed in
the Pieniak et al. and other patents noted above.
Thus, the composite web W' is useful apart from this
invention, as an absorbent article of a type
disclosed in the Pieniak et al. patents noted above.
According to this invention, however, the
composite web W', after any such intermediate
processing step has been completed, is moved to a
grinding zone Z3, in which the composite web W' is
ground, as by means of a grinding mill (not shown),
so as to form the first and second particles. At
least some of the dispersed particles retained by the
composite web W' are broken, as the composite web W'
is ground, so as to produce the first particles from
the broken particles that had been bound t-o fibers
from the fibrous web W', from any broken particles
that had been retained by the composite web W' but
were not bound to fibers from the fibrous web W, and
fx~m any particles that had been retained by the
composite web W' but were not bound to fibers from
the fibrous web W and were not broken, and so as to
form the fragments bound to fibers from the fibrous
web W from the broken particles ~hat had been bound
to fibers from the fibrous web W and from any
particles that had been bound to fibers from the
fibrous web W but were no~ broken.
-
Preferably, the absorbent mixture A
comprises, on a weight basis, about 5 to 40% offibers from the fibrous web W, more preferably about
10% of fibers from the fibrous web W, with the
balance consisting essentially of a superabsorbent
polymer. More preferably, the absorbent mixture A
lS comprises, on a wei~ht basis, about 10~ of fibers
from the fibrous web W, also abQut 30 to 80% of the
superabsorbent polymer, most preferably about 50% of
the superabsorbent polymer, as particles, i~e.,
powder or granules, and about 10 to 60% of the
superabsorbent polymer, most preferably about 40% of
the superabsorbent polymer, as fragments bound to at
least some fibers from the fibrous web W. A most
preferred compositi~n for the absorbent mixture A, on
a weight basis, is~ therefore, about 10% of fibers
from the fibrous web , about 50~ of the
superabsorbent polymer, as particles, i.e., powder or
granules, and about 40~ of the superabsorbent
polymer, as fragments bound to at least some fibers
from the f ibrous web W.
When the composite web W is ground,
fragments of ~he polymerized, cross linked material M
remain bound to fiber~ from the fibrous web W and
strengthen the fiber~ to which such fragments are
bound~ Particles produced by grinding of the
3~ composite web W' with fibrous phases includin~ such
g~ ~
-13-
strengthened fibers tend tG retain their bulk when
wetted with a liquid being absorbed by the
polymerized, cross-linked material ~, e.g., with
urine being absorbed in a disposable diaper~ 5ince
the liquid can channel through the absorbent mixture
by capillary action to be then absorbed by the
polymerized, cross-linked material M, the absorbent
mixture A exhibits superior wicking properties with
less tendency for gel blockinq, whieh is explained
ab~ve.
Furthermore, the absorbent mixture A
exhib;ts superior absorbent properties, not only in
terms of its efficiency as absorbent material but
also in terms of its rate of absorbency, as compared
to a composite web comprising fibers of the same
types and in the same ratios and a superabsorbent
polymer of the s~ne type, for equivalent basis
weights of the s~perabsorben~ polymer.
As shown fragmentarily in ~IGURE 2, an
absorbent article 10 useful in a disposable diaper
having conventional backing and facing layers (not
shown) comprises a relatively thi~k, nonwoven fibrous
layer 12 of fibers from comminuted wood pulp, a
relatively thick layer 14 of a ground, absorbent
mixture according to this invention, in intimate
contact with the fibrous layer 12~ an intermediate
layer 16 of a composite web similar to the ccmposite
web described above, in in~imate contact with the
layer 14 of the absorbent mixture, and a relatively
thin, nonwoven, fibrous layer 18 of fibers from
comminuted wood pulp. ~n ~I~RE 2, the intermediate
layer 16 of a composite web ~nd the layer 14 of the
absorbent mixture are demarcated approximately by
dashed lines.
201673
--14--
As one example, the absorbent article 10 may
be advantageously made by casting the relatively
thin, nonwoven, fibrous layer 18 with a basis weight
of 2.6 oz/yd2 onto one expansive surface of the
S composite web to constitute the intermediate layer
16, such web having a basis weight of 1.2 oz/yd2
and an add-on ratio of 3:1, inverting the resulting
two-layer structure, distributing the relatively
thick layer 14 of the ground, absorbent mixture with
a basis weight of 9.7 oz/yd2 after grinding onto
the opposite surface of the fibrous layer 18, and
casting the relatively thick, nonwoven, fibrous layer
12 with a basis weight of 5.2 oz/yd2 onto the
exposed, expansive surface of the layer 14 of the
lS ground, absorbent mixture Desirably, the relatively
thin, nonwoven, fibrous layer 18 tends to retain any
small particles that tend to sift from the layer 14
of the ground, absorbent mixture through the
composite web constituting the intermediate layer
2~ 16. In the example, the ground, absorbent mixture
results from grinding a composite web with a basis
weight of 1.2 oz/yd2 and an add-on ratio of 10:1,
before grinding. The composite web to constitute the
intermediate layer 16 may be pre-compressed, i.e.,
compressed before the relatively thin, nonwoven,
fibrous layer 18 is cast. All basis weights noted
above are approximate.
Altho~gh the absorbent article 10 has been
described as having layers, it is to be here
understood that the materials of such layers tend to
commingle. As an example, some of the ground,
absorbent material of the layer 14 tends to ~igrate
into the fibrous structure of the composite web
constituting the layer 16. All references herein to
3S layers are intended to be so understood.
-15-
ln the absorbent art;cle 10, the fibrous
layers 12, 18, are regarded as wicking layers even if
either such layer tends to remain dry t whereas the
layers between the f ibrous layers 12, 18 are regarded
5 as absorbing layers. Such designations of layers as
wicking layers and absorbing layers are not intended
as lim;ting, however, since the fibrous layers 12,
18, ordinarily exhibit some absorbency and the fibers
of the layers between the fibrous layers 12, 18, have
good wicking capabilities. The absor~ent article 10
exhibits a gradient of different absorbencies at its
respective layers. In a disposable diaper t the
thicker, fibrous layer 12 is to be preferably
disposed so as to face the backing layer, which is
liquid-impervious, not the facing layer, which is
liquid-pervious.
For comparable amo~nts of a superabsorbent
polymer, the absorbent article 10 provides numero~s
advantages over absorbent articles known heretofore.
Thus, the absorbent article 10 exhibits a faster rate
of absorbency, which may be plausibly explained by
different rates of absorbency within the absorbent
article 10, particularly in the ground, absorbent
material constituting the layer 14 and the composite
web constituting ~he layer 16. Also, the absor~ent
article 10 exhibits less leakage~ which may be
similarly explained. A greater portion of the
s~perabsorbent polymer tends to contact the fibrous
material of ~he absorbent article 10, particularly
the relatively thick, nonwoven, fibrous layer 12?
which acts as a wicking layer. The relatively thin,
nonwoven, fibrous layer 18 tends to remain drler.
Moreover, the superabsorbent polymer tends
to swell to a higher capacityO which tends to be less
restricted by the fibro~s materials, particularly in
the ground, absorbent material ronstituting the layer
14. The higher capacity of the superabsorbent
polymer provides the absorbent artiele 10 with a
higher capacity and with less tendency to leak.
S F~rthermore, since much of the superabsorbent polymer
is present in the ground, absorbent material
constitutin~ the layer 14, rather than in the
composite web constituting the layer 1~, there is
less need for softening, cr tenderizing, to condit;on
the absorbent article 10 for its use in a disposable
d i aper .
As developed from comparative tests, FIGI)RE
3 is a graph plotting, for each of two samples,
absorbency of a test liquid vers~s time. The test
liquid, for each of these samples, was an aqueous
solution of 1% by weight of sodium chloride.
Absorbency was measured as demand absorbency, under a
sample pressure of 0.5 psig and a 1.5 cm negative
head of the test liquid. The absorbed volume was
measured after one minute and after three, five,
nine, twenty, and thirty minutes, as indicated on the
graph. Demand absorbency was measured as described
in McConnell V.S. Patent No. 4,357,~27.
In FIGURE 3, the upper plot represents a
2~ first sample, of an absorbent mixture according to
this invention, as made from ~ fibrous web comprising
fibers of a type having a hollow core, as available
commercially under the trademark HOLLOFIL from E. I.
DuPont de Ne~ours and Company~ Wilmington, Delaware,
as carded into a nonwoven web having a basis weight
of 1.2 oz/yd2 and thermally bonded by subje~ting
the nonwoven web to air heated to about 275F and
pulled through the nonwoven web while the nonwoven
web was supported on B screen, and an aqueous
solutio~ of 65~ concen~ration (by weight) of a 55
neutralized (on a mole basis) potassium salt of
acrylic acid, as neutralized with a 45% potassium
hydroxide solution.
The fibrous web was flo~ded with the aqueous
S solution, while the fibrous web was supported on a
screen; so as to saturate the fibrous web. The
saturated web was exposed to a partial vacuum, which
re~oved excess amounts of the aqueous solution.
The material in the aqueous solution was polymerized
and cross-linked in situ, within the fibrous web, so
as to form a composite web. The ~aterial in the
aqueous solut;on was polymerized and cross-linked by
electron beam irradiation with an initial exposure ~f
2 MRAD on each side of the fibrous web and with a
curing dose of 8 MRAD on each side of the fibrous
web.
The composite web was ground into
particulates, so as to form the first sample, which
on a weight basis consisted essentially of about 10~
of the fibers from the fibrous web, about 50% of the
polymerized, cross-linked material, as particles, and
about 40% of the polymerized, cross-linked material,
as fragments bound to at least some fibers from the
fiberous web. The polymerized, cross-linked material
present in the first sample is a typical example of a
superabsorbent polymer, as used in disposable diapers
and other products requiring high absorbency.
In ~I~JRE 3, the lower plot represents a
second sample, which consisted essentially of a
composite web containing polymerized, cross-linked
material like the composite web containing
polymerized, cross-linked material in the first
~ample, the polymerized, cr~ss~inked material in the
second sample having a ba~is weight about equal to
the basis weight of the polymerized, cross-linked
'J.~
~ 18-
material present in the first sample. The second
sample was not ground into particulates.
It has been concluded~ from the results
plotted in FIGURE 3, that an absorbent mixture
S according to this invention has superior absorbent
properties, not only in terms of its efficiency as
absorbent material but also in terms of its rate of
absorbency, as compared to other structures
containing a superabsorbent material of the same
type, for equivalent basis weights of the
super absorbent material.
From the foregoing, it will be observed that
numerous modifications and variations can be efected
without departing from the true spirit and scope of
the novel concept of the present invention. It is to
be understood that no limitation with respect to the
specific embodiment illustrated herein is intended or
should be inferrecl. The disclosure is intended to
cover by the appended claims all such modifications
20 as fall within the scope of the claims.
''5
